1. Field of the Invention
The present invention relates generally to paint film thickness of painted bodies and, more specifically, to a system for automatically measuring paint film thickness of painted bodies.
2. Description of the Related Art
The application of paint to a body of a vehicle is a sensitive process. The quality, durability, and color matching of the paint are critical in producing a high quality product, and therefore require significant quality control efforts. Generally, paint film thickness is monitored by use of hand-held sensors, such as an ultrasonic pulse echo layer thickness (PELT) meter or a magnetic induction meter. These sensors are handled by an operator who must manually apply the sensor against a surface of the body of the vehicle in a position normal to the surface at a plurality of locations on the surface. In the performance of this measurement, it is highly important that the operator position the sensor normal to the particular location being sensed, and it is also critical that the operator position the sensor consistently at the same locations on the surface being sensed. Errors in the angle of the sensor relative to the surface or in the location of the sensor on the surface can adversely affect quality control. Presently, readings are taken manually by an operator, which is time consuming and does not provide sufficient information or sample size to control the paint process. Because a significant reliance is placed upon the operator, a significant amount of error is introduced in the quality control of the paint process.
It is also known to provide a method and apparatus for positioning sensors against a non-planar surface for sensing paint film thickness. An example of such a method and apparatus is disclosed in U.S. Pat. No. 5,959,211 to Wagner et al., the disclosure of which is hereby incorporated by reference. In this patent, the apparatus includes a movable fixture and a plurality of pistons carried by the movable fixture. Each of the pistons is movable independently with respect to the fixture. Each piston includes a distal end and a sensor pivotally mounted to each distal end. Each distal end is spring-biased away from the fixture. Each sensor includes at least two contact points for contacting the non-planar surface on opposing sides of the respective location for orienting the sensor in a position normal to the non-planar surface at the respective location. However, the film thickness is only measured on two vehicle bodies per day and the paint process cannot be controlled with this data.
As a result, it is desirable to provide a system for automatically measuring paint film thickness of painted bodies for closed loop control of the paint process. It is also desirable to provide a system to measure multiple layers of paint film automatically to control the paint process for each layer, which will result in closed loop control of the paint process. It is further desirable to automatically control the paint process to improve paint quality, reduce material costs, and provide a better surface appearance.
Accordingly, the present invention is a system for automatically measuring paint film thickness of painted bodies for closed loop control of a paint process. The system includes a cell for receiving painted bodies from the paint booth and a conveyor control system for controlling the movement of painted bodies between the paint booth and the cell. The system also includes an AutoPelt system communicating with the conveyor control system for measuring paint film thickness of the painted bodies in the cells. The system includes an integrated paint quality control (IPQC) monitoring system communicating with the AutoPelt system for receiving data of paint film thickness information and combining the paint film thickness information with automation parameters on a vehicle identification number (VIN) basis of the painted bodies to control paint automation equipment of the paint booth.
One advantage of the present invention is that a system for automatically measuring paint film thickness of painted bodies is provided for closed loop control of the paint process. Another advantage of the present invention is that the system automatically measures paint film thickness, which is used as feedback information to control the paint process. Yet another advantage of the present invention is that the system automatically controls the paint process significantly, improving paint quality, reducing material costs, and providing a better surface appearance on the painted body of the vehicle.
Other features and advantages of the present invention will be readily appreciated, as the same becomes better understood, after reading the subsequent description taken in conjunction with the accompanying drawings.